Group 7, the halogens Flashcards
describe the physical appearance of the halogens
chlorine
bromine
iodine
chlorine -yellow green gas
bromine - dark red
iodine - dark grey solid
why do not we study fluorine and astatine in the lab ?
F
At
F - too dangerous
At - highly radioactive
write the balanced symbol equation for the reaction between magnesium and bromine
Mg (s) + Br2 (aq) -> MgBr2 (g)
- magnesium is oxidized
- bromine is reduced
write the ionic equation for the oxidation of iron(II) ions in solution to iron(III) ions by aqueous chlorine
2Fe2+ (aq) + CI2 (aq) -> 2Fe3+ (aq) + 2CI- (aq)
why cant iodine iron(II) ions compounds ?
only capable of oxidizing iron to the +2 oxidation state
reactions with non metals
- when heated with hydrogen
chlorine
bromines
iodine
chlorine - colorless acidic gas
bromine - pale blueish flame
iodine - reversible reaction
what is the test for halide ions
- place potassium chloride to a height of 1cm into a test tube
- add silver nitrate until precipitate forms
- add twice the volume of dilute ammonia, stopper and shake
- if the precipitate remains, add conc. ammonia in the fume cupboard and shake carefully
- repeat with potassium bromide and potassium iodide
colour of the precipitate with AgNO3
chloride
bromide
iodide
chloride - white
bromide - cream
iodide - yellow
solubility of these in dilute ammonia
chloride
bromide
iodide
chloride - ppt dissolves
bromide - ppt remains
iodide - ppts remains
state the observations and products of NaCI + conc. H2SO4
-colourless acidic gas forms that fumes in moist air (HCI)
-white solid remains (NaHSO4)
what type of reaction is NaCI + conc. H2SO4
acid base reaction so no redox
state the observations and products of NaBr + conc. H2SO4
-orange vapour (SO2) mixed with colourless acidic gas
-solid product is NaHSO4
-some HBr is formed
what type of reaction is NaBr + conc. H2SO4
redox reaction
- the bromide ions is oxidised to bromine and the sulphur is reduced from +6 to +4
- acid base reaction
-HBr forms
state the observations and products of NaI + conc. H2SO4
- a dark solid forms which gives off a purple vapour on warming O2
- some yellow solid may be seen and there is a bad egg smell
what type of reaction is NaI + conc. H2SO4
redox reaction
- iodide ions are oxidised to iodine and the sulphur is reduced from +6 to 0 -2
oxidising power - define
a measure of the strength with which an atom is able to attract and capture an electron
reducing power - define
a measure of the tendency of an atom or ion to donate an electron
list three properties the hydrogen halides have in common
- strong acids so ionise completely
- very soluble in water
- colourless gases at room temperature which fume in moist air
write the balanced symbol equation for the reaction between ammonia and hydrogen chloride gas
NH3 (g) + HCI (aq) -> NH4CI (s)
- would would see white smoke
making bleach - disproportionation reaction
CI2 (g) + 2OH (aq) -> CIO- (aq)+ CI- (aq) + H2O (l)
what is the boiling point of halogens as we go down the group ?
increases bc the london forces increase due to the increasing size and relative mass of the atoms
what is the physical state of group 7 at the top n bottom ?
gas at the top
solid at the bottom
what is the electronegativity as you go down the halogens ?
decreases bc the atoms get larger and the distance between the positive nucleus and bonding electron increases - more shielding
when undertaking halogen displacement reactions what can we add to see the colour change easily ?
organic solvent like hexane
what form if the halogen present will dissolve readily in a displacement reaction ?
organic solvent above the aqueous layer - a coloured band will appear
the more reactive halogens will displace in a more/less reactive halide ions ?
less
as we go down the group is the halogens less/more oxidising ?
less
what happens if addition of chlorine water (almost colourless) + potassium chloride solution (colourless) ?
no reaction
what happens if addition of chlorine water (almost colourless) + potassium bromide solution (colourless) ?
Aq - yellow
Org - orange
what happens if addition of chlorine water (almost colourless) + potassium iodide solution (colourless) ?
Aq - brown
Org - purple
what happens if addition of bromine water (almost colourless) + potassium chloride solution (colourless) ?
no reaction
Aq - yellow
Org - orange
what happens if addition of bromide water (almost colourless) + potassium bromide solution (colourless) ?
no reaction
Aq - yellow
Org - orange
what happens if addition of bromine water (almost colourless) + potassium iodide solution (colourless) ?
Aq - brown
Org - purple
what happens if addition of iodide water (almost colourless) + potassium chloride solution (colourless) ?
no reaction
Aq - brown
Org - purple
what happens if addition of iodide water (almost colourless) + potassium bromide solution (colourless) ?
no reaction
Aq - brown
Org - purple
what happens if addition of iodide water (almost colourless) + potassium iodide solution (colourless) ?
no reaction
Aq - brown
Org - purple
what are the uses of sodium chlorate ?
treating water
bleaching paper and fabrics
cleaning agents
what does chlorine do when added to water ?
kill bacteria
water sterilisation - chlorine
H2O + CI2 <-> HCI + HCIO
- chlorine has been simultaneously reduced and oxidised
why is I- more powerful reducing agent than F- ?
the outer electron is lost more readily
what does hydrogen halides form when dissolved in water ?
acidic solutions
when hydrogen halides react with water in the air what does it form ?
white misty fumes
test for ammonium compounds
add sodium hydroxide gently heat, and if ammonium compounds gas will be produced
test for hydroxides
hydroxides are alkaline and they will turn red litmus blue
why is HCI a good conductor of electricity ?
the covalent bond in hydrogen chloride changes to ionic bond in aqueous solutions
